A standard collet chuck for attachment to a mounting collar of a tool or workpiece has as described in German patent documents 4,138,974 of E. Brangs and F. Kuckelsberg and 299 22 642 and in U.S. Pat. No. 5,865,578 a body formed centered on an axis with a forwardly open socket shaped to coaxially receive the mounting collar. A collet inside the body has a plurality of jaws with front ends that project axially forward into the collar. The jaws can rock to move the front ends radially outward, or in some situations inward, to engage behind an axially forwardly directed shoulder of the collar and thereby lock the collar to the chuck body. Each jaw can pivot in the body about a respective axis extending in a plane perpendicular to the axis and offset therefrom. An axially displaceable cam sleeve inside the body has a radially directed front cam surface engageable with front inner faces of the front ends of the jaws and a radially oppositely directed rear cam surface engageable with rear faces of rear ends of the jaws. Thus, when displaced axially rearward, the cam sleeve radially shifts the front ends of the jaws to hold the workpiece and, when displaced axially forward, rocks these front ends oppositely to release the workpiece.
It is further known, for example from German utility model 299 21 999 to use the actuating shaft of the collet chuck to axially shift or knock out the tool or workpiece from the chuck after it is released. Thus after moving through enough of a stroke to release the jaws holding the tool or workpiece, the shaft end bumps against the tool or workpiece and pushes it slightly out of the chuck so that it can be grabbed, normally by an automated loading/unloading device.
The problem with these chuck actuators is that they are too fast. They must be pressurized with great force to overcome the pressure of the springs that normally hold the chuck clamped on the tool or workpiece, so that they move rapidly and strike the tool or workpiece forcibly. The result can be axially shifting the tool or workpiece through too great of a distance, so that the automatic loading/unloading device cannot properly grip it, or even so that it actually shoots out of the chuck and drops away.